Core Summary: The Clinical Core seeks to improve the diagnosis and management of individuals with Parkinson disease (PD) through its support of the JHU Udall Center and Clinical Project 4. With this funding period request, the Clinical Core will focus on ascertainment of blood at every visit and expansion of its brain autopsy program to include gut and vagal nerve tissue. The collection of blood from individuals who undergo autopsy, coupled with the longstanding follow up of those individuals, uniquely situates the Clinical Core to allow the Clinical Project to identify PD biomarkers. To ensure that the Clinical Project has sufficient blood to complete its aims, the Clinical Core will also be responsible for obtaining blood through collaborations with other cohorts both within and outside JHU.